5.5

Enzymes are proteins that speed up specific reactions in cells.



Enzymes and Activation Energy

-To start a chemical reaction, first need to weaken the chemical bonds

-molecules to absorb energy.

activation energy- start up energy



one way - heat up the mixture of molecule *then activation energy is produced*

Hot molecule colide with cooler molecule weakens the bond.



cellular reactions depend on the assistance of catalysts

catalysts-compounds that speed up chemical reactions.



enzymes-the main catalysts of chemical reaction in organisms are specialized proteins

enzymes provied a way for reactions to occur at the cell's normal temp.

enzyme do not supply activation energy to the reacting molecule, but lowers the energy requirement barrier so that the reaction can proceed at normal cell temp.



How Enzyme Work

A substrate binds to an enzyme at an active site. The enzyme-substance interaction lowers the activation energy required for the reaction to proceed. In this example, water is added to the weakened bond in sucrose, breaking sucrose into glucose and fructose.
CONCEPT CHECK:
1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?
Activation energy in a reaction starts up the required molecules to get energy which is to trigger a chemical reaction and activate the reactants which allows a chemical reaction to happen. An enzyme affects activation energy because it helps to speed up cellular reactions and provides a way for reactions to occur at cell's normal temperature.
2. Describe how a substrate interacts with an enzyme.
A substrate interacts with an enzyme by helping this specific reactant fit into a particular region, the active site. When it fits in the active site, the active site changed slightly, fitting the substrate better.